Extension Versioning (The GNU Awk User’s Guide)

From Get docs
Gawk/docs/latest/Extension-Versioning API Version Constants and Variables

The API provides both a “major” and a “minor” version number. The API versions are available at compile time as C preprocessor defines to support conditional compilation, and as enum constants to facilitate debugging:

API Version C Preprocessor Define enum constant
Major gawk_api_major_version GAWK_API_MAJOR_VERSION
Minor gawk_api_minor_version GAWK_API_MINOR_VERSION

Table 17.3: gawk API version constants

The minor version increases when new functions are added to the API. Such new functions are always added to the end of the API struct.

The major version increases (and the minor version is reset to zero) if any of the data types change size or member order, or if any of the existing functions change signature.

It could happen that an extension may be compiled against one version of the API but loaded by a version of gawk using a different version. For this reason, the major and minor API versions of the running gawk are included in the API struct as read-only constant integers:

The major version of the running gawk.
The minor version of the running gawk.

It is up to the extension to decide if there are API incompatibilities. Typically, a check like this is enough:

if (   api->major_version != GAWK_API_MAJOR_VERSION
    || api->minor_version < GAWK_API_MINOR_VERSION) {
        fprintf(stderr, "foo_extension: version mismatch with gawk!\n");
        fprintf(stderr, "\tmy version (%d, %d), gawk version (%d, %d)\n",
                api->major_version, api->minor_version);

Such code is included in the boilerplate dl_load_func() macro provided in gawkapi.h (discussed in Boilerplate Code).